Why has Android started giving such long Connection Intervals?

[awneil]

We use the Nordic UART Service in development to get some diagnostic data out of our device to an Android app.

Until recently, Android has been happy to grant a connection interval of 16 (ie, 16x1.25ms = 20ms), or even less.

But now, Android seems reluctant to ever go below 39 (ie, 39x1.25ms = 48.75ms).

Has anyone else noticed this?

Is there any way to "persuade" Android to grant a faster rate?

16 is about the minimum we require.

We are using nRF8001.

Update:

When we started this, around last October, this is what we were getting with the Nordic Bandwidth Test example (part of the Nordic ble-sdk-arduino):

Note Connection Interval = 9.

[AmiguelS]

Are you perhaps using a different phone or Android version? The supported Connection Interval (CI) and the number of packets sent per CI vary greatly, as presented in this post.

[awneil]

No - it is on tablets (mostly; and a few phones) that have been used throughout the project.

Yes, they do vary greatly.

[Petter Myhre]

My impression is that Nexus phones prefer longer intervals, while Samsung phones allow shorter intervals. From Android 5 it has been possible to request a connection priority, if you use connection priority high I think you should get 11.25-15ms connection interval. You can test this feature with nRF Connect for Android, when you have connected click on the vertical ... and select request connection priority.

[awneil]

We have found the opposite - my Nexus gives "better" results than the client's Samsung tablet!

Could you elaborate on "connection priority" - is that an Android thing?

[Petter Myhre]

Yes. It's an Android thing. See this.